Partial obstruction arrangement for preventing plug formation in a shutdown slurry pipeline

ABSTRACT

Method and apparatus for preventing plug formation in a shutdown slurry pipeline. A plurality of partial obstructions are positioned in the pipeline in those sections of the line where inclination exceeds some predetermined critical angle to prevent the formation of a line plug by interrupting slumping of the solid phase of the slurry material.

Unite States Patent inventor Moye Wicks, Ill

Houston, Tex.

Appl. No. 860,352

Filed Sept. 23, 1969 Patented Sept. 14, 1971 Assignee Shell Oil Company New York, N.Y.

PARTIAL OBSTRUCTION ARRANGEMENT FOR PREVENTING PLUG FORMATION IN A SHUTDOWN SLURRY PIPELINE 9 Claims, 9 Drawing Figs.

US. Cl 302/64, 302/14 Int. Cl B65g 53/34 Field of Search 302/14, l5, 16, 64, 66

[56] References Cited UNITED STATES PATENTS 630,605 8/1899 Gordon et al 302/64 3,313,577 4/1967 Wolfe 302/64 Primary ExaminerAndres H. Nielsen Anorneys-Thomas R. Lampe and J. H. McCarthy ABSTRACT: Method and apparatus for preventing plug formation in a shutdown slurry pipeline. A plurality of partial obstructions are positioned in the pipeline in those sections of the line where inclination exceeds some predetermined critical angle to prevent the formation of a line plug by interrupting slumping of the solid phase of the slurry material,

PARTIAL OBSTRUCTION ARRANGEMENT FOR PREVENTING PLUG FORMATION IN A SHUTDOWN SLURRY PIPELINE The present invention relates to pipeline transport operations; and, more particularly, to a method for preventing plug formation by terminating the downward movement of slurry solids in an inclined portion of pipeline under the influence of gravity during a shutdown period.

Transportation by pipeline is a major and growing industry. With the use thereof formerly confined almost entirely to movement of water, gas and petroleum products, pipelines, with the advent of slurry transport, have become useful for long and short hauls of a wide variety of raw materials and finished products.

With respect to the pipeline transportation of materials in slurry form, problems arise when such materials are moved through pipelines inclined to go over a hill or down into a valley. At these locations, during a planned or emergency line shutdown, the solids of the transported slurry may settle out vertically and subsequently slide down the inclined portions of the pipeline, thereby causing a compacted plug which may be very difficult to dislodge and move when line shutdown is terminated and transport activities are resumed.

These difficulties are most commonly avoided by laying solids-carrying or slurry pipelines so that they do not exceed a slope or angle of inclination below which sliding does not occur. Alternatively, the inclined pipeline sections are emptied at each shutdown. Obviously, these alternative prior art approaches are not always feasible or economical, especially in those situations where long and relatively steep slopes are encountered. Slopes of this nature are being encountered with increasing frequency as pipeline operations are being extended to new relatively inaccessible mountainous areas in the United States and elsewhere.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved and economical method and apparatus whereby slurry solid phase material being transported in an inclined pipeline section is prevented from slumping during a line shutdown in such a manner as to form a plug.

This and other objects have been attained in the present invention by providing a method and apparatus for preventing plug formation in a shutdown slurry pipeline wherein a plurality of partial obstructions are installed in the pipeline in the sections where the inclination exceeds some critical angle below which slumping does not occur. The obstructions, which may take the form of plates secured to the bottom inner surface of the pipeline, for example, prevent the settled bed of the slurry solid phase from sliding down the inclined portion of the pipeline to form a plug.

DESCRIPTION OF THE DRAWING The above-noted and other objects of the present invention will be understood from the following description, taken with reference to the accompanying drawing. In describing the invention in detail, reference will be made to the drawing in which like reference numerals designate corresponding parts throughout several views in which:

FIG. I is a diagrammatic view illustrating a given length of slurry pipeline which has been modified in accordance with the teachings of the present invention;

FIG. 2 is an enlarged cross-sectional view in longitudinal projection illustrating an inclined portion of the pipeline section of FIG. 1 with partial obstructions installed therein;

FIG. 3 is a cross-sectional view of the pipeline taken along line 3-3 of FIG. 2;

FIG. 4 is a view similar to that of FIG. 3 but illustrating an alternative form of partial obstruction;

FIG. 5 is a view similar to that of FIG. 3 illustrating an additional alternative form of partial obstruction;

FIG. 6 is a cross-sectional side view showing a detail of the apparatus shown in FIG. 5;

' rangement in differing stages of the operation thereof.

Referring now to FIG. 1, a given length of slurry pipeline I1 is illustrated in the position assumed thereby as the pipeline proceeds to and from a valley formed between two hills or mountains l2 and 13. The terrain illustrated is typical of that encountered in pipeline laying activities, although it should be understood that the teachings of the present invention may be carried out in any topographical configuration wherein a portion of slurry pipeline is inclined.

The transportation of slurries consisting of solid particles in a fluid medium by use of pipelines similar to that disclosed in FIG. 1 is quite well known, and such expedient is finding increasing use, especially in those situations where the source of raw materials is relatively remote and inaccessible from the point of delivery, which may be a suitable processing plant, for example. In the disclosed arrangement, it may be assumed for purposes of illustration that the slurry material being transferred through pipeline 11 as by means of conventional pumps (not shown) is moving through the line in the direction indicated by the arrows. However, the teachings of the present invention are, of course, applicable regardless of the direction of flow of slurry.

As long as flow continues in the pipeline, the solid matter of the slurry will remain in suspension within the pumped liquid, even when the solid matter has a higher specific gravity than the liquid. If, however, the flow is stopped for any reason, i.e., the pipeline is shut down, such solid matter will settle out of suspension. In the situation where the line is horizontal or the slope of the line is insufficient to cause sliding of the settled solids, no problem is created by such settling out. Under these conditions, a liquid-rich channel remains open at the top of the line which allows the settled material to be resuspended with a minimum of difficulty upon resumption of slurry flow.

A serious problem can exist when the pipeline must be inclined to go over a hill or down a valley, as illustrated, for example, in FIG. 1. At these locations, the settling of solids followed by their sliding down the slope during a protracted shutdown can result in a compacted plug of material difficult, if not impossible, to move or resuspend. In the illustrated pipeline configuration, such solids would slide downwardly into the valley formed between hills or mountains l2 and 13. The solid material would then compact under its own weight to form a plug in the valley in an obvious manner.

Such plug formation is prevented in accordance with the teachings of the present invention as follows. Installed within pipeline 11 at preselected locations are a plurality of partial obstructions in the form of plates 21-28 either secured to the bottom inner wall of pipeline 11 and extending substantially at right angles to the pipeline throughbore 31 or introduced as segmental valve blockages. FIG. 2 illustrates these partial obstructions in greater detail and reference may be had to that figure as well as FIG. 1 for a proper understanding of the operation of one form of partial obstruction which may be utilized in carrying out the teachings of the present invention. Plates 2128 may be, for example, secured to pipeline 11 in any known manner as by means of welding, and extend into the throughbore 31 defined by pipeline 11 a predetermined distance such that normal slurry transport activities are not unduly impeded while at the same time being capable of performing the desired antislumping function in a manner to be described in greater detail below.

The plates or segmental valves which are utilized in carrying out the teachings of the present invention are installed only in those portions of the pipeline which are inclined with respect to the horizontal at an angle equal to or greater than some predetermined angle 0 at which slumping of the solid phase of the slurry material carried by pipeline 1]. occurs. This angle would, of course, depend upon such factors as viscosity of the slurry material, relative densities of the solid and liquid phases of the slurry, etc.

In the event pipeline 1 1 is shut down for any reason, such as repair work, inspection, etc., the solid phase of the slurry material, normally being of greater density than the liquid phase thereof, tends to settle out to form a bed on the bottom of pipeline 1]. In the event such settling out occurs in the portions of the pipeline inclined to the horizontal, at an angle greater than 0, the solid phase tends to slump or slide downwardly within the pipeline. If this slumping action is not prevented, a plug of solid phase slurry material may be formed in the lowermost portions of the pipeline which may prevent restart of the pipeline. By installing partial obstructions such as plates 21-28 in those portions of the pipeline inclined at an angle greater than 6, such slumping is prevented due to the fact that the settled bed of solid phase slurry material 42 contacts the plates (FIG. 2), thus preventing further downward movement thereof within the pipeline.

Plates 21-28 may have any desired cross section. In FIG. 3, for example, one representative plate 26 is shown as being in the form of a half moon. In FIG. 4, an alternative form of plate 26A is illustrated as forming a segment of a circle defined at the top thereof by a chord lying at right angles to the pipeline throughbore and extendinga predetermined distance into the pipeline, and defined at the bottom thereof by the inner periphery of the pipeline. Once again, the plates would be installed only in those portions of pipeline 11 where the angle with respect to the horizontal exceeds angle with the number thereof per given length of pipe being selected based on such factors as the amount of slurry solid phase material, angle of pipeline inclination, etc.

FIGS. 5 and 6 illustrate an alternative embodiment of the apparatus according to the present invention. Rather than employ fixed plates as the partial obstruction in the pipeline, a plurality of plate segments 51 are shown as being pivotally mounted at selected locations along the bottom of pipeline 11. Plate segments 51 are mounted on conventional hinges 52 (FIG. 6) so that they readily pivot in the direction of slurry flow under slurry pressure during pipeline transport activities to lay substantially flat against the inner wall of pipeline 1 1 (as shown by the broken lines in FIG. 2). As slurry transport terminates, a biasing means such as springs (not shown) associated with hinges 52 bring the plates to a fully upright position (as shown by the solid lines in FIG. 2) whereby downward slumping of slurry solid phase material will be prevented. Stop elements 53 are preferably integrally attached to plates 51 to prevent further movement of the plated by contacting pipeline 11 in an obvious manner. Upon resumption of slurry transport, the plates 51 will again flatten against the pipeline inner wall, thereby providing a minimum of slurry flow resistance. In FIG. 7 an arrangement similar to that disclosed in FIGS. 5 and 6 is shown with the difference being that a plurality of pivotally mounted and biased plates 61 are disposed about the complete inner periphery of pipeline 11.

FIGS. 8a and 8b illustrate still another form of partial obstruction arrangement which might be utilized in carrying out the teachings of the present invention. Secured in a fluidtight manner to the upper portion of pipeline 11 in a location where slumping is likely to occur is a housing member 61 in the form of an elongated upstanding cylinder and defining an interior in communication with the throughbore defined by pipeline 11. The upper portion of housing member 61 is closed by means of a cap 62 having a vent hole 63 therein which provides communication between the ambient atmosphere and the interior of cylinder 61. A piston element 64 is slidably mounted within housing member 61 with suitable seal elements being provided thereabout to enable the piston element 64 to move freely up and down within the housing member while at the same time providing a fluidtight seal between the piston element and the inner wall of the housing member. A shaft 65 is secured to piston 64 and extends downwardly therefrom. Affixed to the free end of shaft 65 is a plate 66 in the form of a semicircle having a curved lower surface conforming to the dimensions of the inner wall of pipeline 11.

As previously stated, the interior of housing member 61 is in communication with the throughbore defined by pipeline 11.

In the disclosed embodiment such communication is provided through a hole formed in the upper portion of the pipeline as at 68. Such hole is surrounded by the walls of housing member 61 in a fluidtight manner and is of sufficient size to permit passage of shaft 65 and plate 66 therethrough. During normal pipeline flow activities the elements of the instant arrangement are in the respective positions shown in FIG. 80 since the pressure of the transported slurry material continually biases piston 64 in an upward direction in an obvious manner. However, as the slurry flow rate diminishes and the pressure within the pipeline drops, piston 64 as well as shaft 65 and plate 66) moves under the influence of gravity in a downward direction until plate 66 contacts the inner wall of pipeline 1] as shown in FIG. 8b. The presence of the plate prevents downward slumping of the slurry solid phase material within the pipeline in an obvious manner. Upon pipeline restart pressures will again rise within the pipeline and hence within the housing member 61 to force piston 64 in an upward direction so that slurry transport within the pipeline may flow in an unimpeded manner until pipeline pressures once again fall below a predetermined minimum. As with the previously described arrangements, this latter approach will be carried out in all those pipeline locations where slumping of the slurry solid phase material is likely to occur.

I claim as my invention:

1. Apparatus for preventing plug formation in a shutdown pipeline utilized to transport slurry material comprising a solid phase and a liquid phase, said plug formation being caused by the slumping and compacting of the slurry solid phase under the influence of gravity, said apparatus comprising:

means positioned in said pipeline at least partially along the inside bottom thereof and extending at substantially right angles with respect to the axis of the throughbore defined by said pipeline and adapted to partially obstruct said throughbore when slurry flow is terminated; and

said means being positioned in said pipeline in those portions of the pipeline which are inclined with respect to the horizontal at an angle at least equal to a predetermined angle at which slumping of the slurry solid phase material under the influence of gravity will occur whereby said slumping is terminated by said slurry solid phase material contacting said means positioned in said pipeline.

2. Apparatus according to claim 1 wherein said means positioned in said pipeline comprises a plurality of plates secured in the interior of said pipeline in a spaced relationship.

3. Apparatus according to claim 2 wherein said plates are in the shape of a half moon.

4. The apparatus according to claim 2 wherein said plates are in the shape of circle segments with each segment being defined at the top thereof by a chord lying at right angles to the pipeline throughbore and at the bottom thereof by the inner periphery of the pipeline.

5. The apparatus according to claim 2 wherein said plurality of plates are segmented and pivotally mounted in said pipeline so that the plate segments lay substantially flat against the inner wall of the pipeline during slurry transport.

6. Apparatus according to claim 1 wherein said means positioned in said pipeline comprises at least one segmental plate adapted to be withdrawn from said pipeline on resumption of flow, thereby minimizing the resistance to slurry flow once flow is resumed.

7. A method of preventing plug formation in a shutdown pipeline utilized to transport slurry material comprising a solid phase and a liquid phase, said plug formation being caused by the slumping and compacting of the slurry solid phase under the influence of gravity, said method comprising:

providing a partial obstruction along the bottom of and substantially at right angles to the pipeline throughbore in those portions of the pipeline where slumping of the slurry solid phase is likely to occur, said partial obstruction interrupting downward movement of the slurry solid phase under the influence of gravity.

8. The method according to claim 7 wherein a plurality of 9. The method of claim 7 including the additional step of partial obstructions are provided at spaced locations in those substantially removing the partial obstruction from the portions of the pipeline where slumping of the slurry solid pipeline upon resumption of slurry flow. phase is likely to occur. 7 

1. Apparatus for preventing plug formation in a shutdown pipeline utilized to transport slurry material comprising a solid phase and a liquid phase, said plug formation being caused by the slumping and compacting of the slurry solid phase under the influence of gravity, said apparatus comprising: means positioned in said pipeline at least partially along the inside bottom thereof and extending at substantially right angles with respect to the axis of the throughbore defined by said pipeline and adapted to partially obstruct said throughbore when slurry flow is terminated; and said means being positioned in said pipeline in those portions of the pipeline which are inclined with respect to the horizontal at an angle at least equal to a predetermined angle at which slumping of the slurry solid phase material under the influence of gravity will occur whereby said slumping Is terminated by said slurry solid phase material contacting said means positioned in said pipeline.
 2. Apparatus according to claim 1 wherein said means positioned in said pipeline comprises a plurality of plates secured in the interior of said pipeline in a spaced relationship.
 3. Apparatus according to claim 2 wherein said plates are in the shape of a half moon.
 4. The apparatus according to claim 2 wherein said plates are in the shape of circle segments with each segment being defined at the top thereof by a chord lying at right angles to the pipeline throughbore and at the bottom thereof by the inner periphery of the pipeline.
 5. The apparatus according to claim 2 wherein said plurality of plates are segmented and pivotally mounted in said pipeline so that the plate segments lay substantially flat against the inner wall of the pipeline during slurry transport.
 6. Apparatus according to claim 1 wherein said means positioned in said pipeline comprises at least one segmental plate adapted to be withdrawn from said pipeline on resumption of flow, thereby minimizing the resistance to slurry flow once flow is resumed.
 7. A method of preventing plug formation in a shutdown pipeline utilized to transport slurry material comprising a solid phase and a liquid phase, said plug formation being caused by the slumping and compacting of the slurry solid phase under the influence of gravity, said method comprising: providing a partial obstruction along the bottom of and substantially at right angles to the pipeline throughbore in those portions of the pipeline where slumping of the slurry solid phase is likely to occur, said partial obstruction interrupting downward movement of the slurry solid phase under the influence of gravity.
 8. The method according to claim 7 wherein a plurality of partial obstructions are provided at spaced locations in those portions of the pipeline where slumping of the slurry solid phase is likely to occur.
 9. The method of claim 7 including the additional step of substantially removing the partial obstruction from the pipeline upon resumption of slurry flow. 